The present invention relates to cleanable, glass fiber ducts for conveying air which are used in heating, ventilating and air conditioning systems.
It is common practice to use glass fiber duct liners in heating, ventilating and air conditioning systems. As discussed in Terry et al, U.S. Pat. No. 4,990,370, column 1, lines 33-50, the interior surfaces of these glass fiber duct liners, which are relatively low in density when compared to glass fiber ducts, are either coated with a rubberized or plastic material or a facing is applied to the surface to prevent portions of the duct liner from breaking away or flaking off due to erosion by the airstream within the duct liner. Without the coating, loose particles of dust and dirt, in the airstream being conveyed, strike the interior surface of the duct liner causing erosion so that portions of the duct liner break away or flake off. However, the coating is only sufficient to prevent the erosion of the interior surface of the duct liner and does not form the smooth, durable surface required to withstand the cleaning of the interior surface of the duct liner by maintenance personnel using conventional commercial or industrial cleaning methods.
Glass fiber airducts are also used in heating, ventilating and air conditioning systems. These airducts are formed from high density glass fiber duct boards having densities of at least 3.5 pounds per cubic foot as compared to densities of about 1.5 pounds per cubic foot for low density duct liners. The duct boards are formed by compressing blankets of resin coated glass fibers to an appropriate thickness and density and curing the resin binder. Due to the high densities and the heavy resin binder contents of the interior surfaces of the duct boards forming the airducts, the high density glass fiber airducts formed from the duct boards do not require coatings or facings on their interior surfaces to prevent the erosion of the interior surfaces of the airducts by airstreams carried by the airducts. However, like the duct liners discussed above, the prior art airducts have not had interior surfaces suitable for cleaning by conventional industrial or commercial cleaning methods.
With recent developments in air quality measurement devices and an overall increase in environmental awareness, there has been an increased interest in the air quality in all types of buildings employing heating, ventilating and air conditioning systems. While in service, especially when the air filtration system is not properly maintained, the interior air conveying surfaces of airducts pick up dust and become increasingly dirty. The accumulation of dust on the interior surfaces of airducts has been identified as a possible nutrient source for microbiological growth. The growth of microbes in a heating, ventilating and air conditioning system may compromise the indoor air quality of the building or home served by the system. Accordingly, there has been a need to provide a cleanable interior surface for airducts.
The interior surfaces of sheet metal airducts are often cleaned with rotating brushes having plastic bristles six inches to a foot in length. Another method of cleaning airducts uses industrial type vacuum cleaners. In addition, it is common to clean the interior surfaces of sheet metal airducts with liquid chemical disinfectants to remove microbiological growth from the interior surfaces of the airducts.
Glass fiber airducts not only effectively convey the air in heating, ventilating and air conditioning systems, unlike sheet metal airducts, glass fiber airducts also provide an acoustical benefit by reducing the transmission of sound. While glass fibers do not support mold growth and the use of liquid chemical disinfectants on the interior surfaces of glass fiber airducts is not necessary, the cleaning of uncoated glass fiber airducts to remove dust and dirt by the methods discussed above can result in damage to the interior surfaces of uncoated glass fiber airducts by puncturing and/or wearing away the interior surfaces of the airducts. Accordingly, there has been a need to provide glass fiber airducts with cleanable interior surfaces that can be cleaned during service by normal commercial or industrial cleaning procedures.